[GitHub] [arrow] emkornfield edited a comment on pull request #8136: ARROW-9078: [C++] Parquet read / write extension type with nested storage type

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emkornfield edited a comment on pull request #8136:
URL: https://github.com/apache/arrow/pull/8136#issuecomment-690411317


   > One gotcha I ran into while using a fixed size list type (nested within another list) that in this case the extension type wasn't preserved. But I suppose this is because the fixed size list is not yet preserved on parquet roundtrip (read back as normal list type), and to add back the extension type, the storage type needs to be the same. So in hindsight, this behaviour is as expected (as long as fixed size list is not yet supported).
   
   @jorisvandenbossche Reading fixed size lists is not yet supported.  One use-case that will likely not be supported in the short term is reading parquet files with FixedSizeLists that have null elements.  Do your use-cases with FixedSizeList allow for null lists?  I would also add that writing FixedSizeLists with null elements only works under a very limited of circumstances today as it is.


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